Embarrassing help.

Okay, so far I've lost quite abit of weight on my low calorie diet *dances*
and its going pretty good, apart from my stomach which isn't flat but Im working on it...
Any way.. Recently like in every 4 weeks or so ill well... okay theres no un-embarrassing way to say this so ill just say it, I can't poop!
Like I haven't..in ages, I only do when ive eaten alot like ALOT.
And Im not doing that cause of my diet.. Also my period, Its gone. Like Im not getting it any more
Im scared Im starting to get anorexia but then again I really don't want to ruin my diet because I'm doing so good at the moment, I mean sure I might not be eating much but Im eating at breakfast, lunch and dinner!
thats quarter of an apple of breakfast, quarter for lunch, a leaf of letuce quarter of a tomato and a couple pieces of surimi for dinner, and I have energy and I don't feel fainty.
thats healthy right? I mean, Im still eating.. I don't understand.